A Hybrid Imperialist Approach in Solving University Timetabling Problems. Information Sciences. Vol. 283, 1-21

Generating timetables for an institution is a challenging and time consuming task due to different demands on the overall structure of the timetable. In this paper, a new hybrid method which is a combination of a great deluge and artificial bee colony algorithm (INMGD-ABC) is proposed to address the university timetabling problem. Artificial bee colony algorithm (ABC) is a population based method that has been introduced in recent years and has proven successful in solving various optimization problems effectively. However, as with many search based approaches, there exist weaknesses in the exploration and exploitation abilities which tend to induce slow convergence of the overall search process. Therefore, hybridization is proposed to compensate for the identified weaknesses of the ABC. Also, inspired from imperialist competitive algorithms, an assimilation policy is implemented in order to improve the global exploration ability of the ABC algorithm. In addition, Nelder–Mead simplex search method is incorporated within the great deluge algorithm (NMGD) with the aim of enhancing the exploitation ability of the hybrid method in fine-tuning the problem search region. The proposed method is tested on two differing benchmark datasets i.e. examination and course timetabling datasets. A statistical analysis t-test has been conducted and shows the performance of the proposed approach as significantly better than basic ABC algorithm. Finally, the experimental results are compared against state-of-the art methods in the literature, with results obtained that are competitive and in certain cases achieving some of the current best results to those in the literature.

Solubilities of solids in supercritical fluids using dimensionally consistent modified solvate complex models

New dimensionally consistent modified solvate complex models are derived to correlate solubilities of solids in supercritical fluids both in the presence and absence of entrainers (cosolvents). These models are compared against the standard solvate complex models [J.Chrastil, J. Phys. Chem. 86 (1982) 3016-3021; J.C. Gonzalez, M.R.Vieytes, A.M. Botana, J.M. Vieites, L.M. Botana, J. Chromatogr. A 910 (2001) 119-125; Y. Adachi, B.C.Y. Lu, Fluid Phase Equilb. 14 (1983) 47-156; J.M. del Valle, J.M. Aguilera, Ind. Eng. Chem. Res. 27 (1988) 1551-1553] by correlating the solubilities of 13 binary and 12 ternary systems. Though the newly derived models are not significantly better than the standard models in predicting the solubilities, they are dimensionally consistent. (C) 2009 Elsevier B.V. All rights reserved.

Comercio exterior : materia y ejercicios

1. Teorías y tendencias del comercio internacional: - Introducción. - Teorías de comercio internacional. - Tendencias actuales del comercio internacional. Cuestiones. 2. Política comercial comunitaria: - La nomenclatura arancelaria y el arancel aduanero común europeo. - Determinación del origen de las mercancías. - Valor en aduana de las mercancías. - Medidas de política arancelaria y comercial: franquicias aduaneras, destinos específicos, suspensiones arancelarias, contingentes y límites arancelarios, contingentes cuantitativos y medidas de defensa comercial. - Regulación de los regímenes de importación y exportación. - Regímenes aduaneros económicos: importación temporal, régimenes de perfeccionamiento activo y pasivo, régimen de transformación bajo control aduanero, zonas y depósitos francos, depósitos aduaneros, cuestiones de política comercial comunitaria y problemas de política comercial comunitaria. 3. Fiscalidad internacional: - I.V.A., II.EE. y la exportación. - I.V.A., II.EE. y la importación. - I.V.A. intracomunitario. - Sistema Intrastat. - Impuesto de sociedades, cuestiones de fiscalidad internacional y problemas de fiscalidad del comercio exterior. 4. Contratación internacional: - Introducción. - Incoterms. 5. Ejercicios de comercio exterior.

Sol-gel combustion synthesis and luminescent properties of nanocrystalline YAG : Eu3+ phosphors

EU3+ -doped Y3Al5O12 (YAG:Eu3+) phosphors were synthesized by a facile sol-gel combustion method. In this process, citric acid traps the constituent cations and reduces the diffusion length of the precursors. YAG phase is obtained through sintering at 900 degrees C for 2h. There were no intermediate phases such as YAlO3 (YAP) and Y4Al2O9 (YAM) observed. The charge transfer band of nanocrystalline phosphors shows a shift toward the high-energy side, compared with that of amorphous ones due to lower covalency of Eu-O bond for nanocrystalline phosphors. The higher concentration quenching in YAG:EU3+ nanophosphors may be caused by the confinement effect on resonant energy transfer of nanocrystalline. It also indicates that the sol-gel combustion synthesis method provides a good distribution of Eu3+ activators in YAG host. (c) 2005 Elsevier B.V. All rights reserved.